2024 and still hard to find a simple spectrum analyzer for linux:
1 voxendo span is NOT available native for Linux (emulation VST did nt work)
2 still no default multiplatform embedded in ardour
3 did nt find ‘renoise’ in the list of plugins in ardour
3 found
but had to build yourself (dozen of deps, PITA)
Prebuilt binaries for x42 plugins are available on his website and in many distributions’ repositories.
What about Linux Studio Plugins (LSP)? LSP offers several spectrum analyzers for different numbers of channels. See tutorial here:
a few more:
ChromaDSP CqtAnalyzer
Jpcima Spectacle
Socalabs Spectrum Analyzer
rty65tt AudioAnalyzer
Calf Analyzer
Another one (waterfall spectrogram) GitHub - wolf-plugins/wolf-spectrum: Real-time 2D spectrogram plugin (LV2, VST and Jack)